Apkii. 13, 1883. 



SCIENCE. 



■211 



ment of a blastoderm in the more rapid division 

 of the germinal cells at the animal pole of the 

 egg ; so that the coarser j'elk-cells become in- 

 cluded bj' the blastoderm, by epibole, just as 

 in the tj-pical meroblastic ovum. The segrega- 

 tion of the protoplasmic and deutoplasmic 

 matter, therefore, occurs after the first cleavage 

 in these types ; in fact, manifests itself after 

 the first and second cleavages in Clepsine and 

 Eana. It is important to note, however, that 

 in the vicinitj- where the polar cells have been 

 extruded, the embryonic or germinal difieren- 

 tiation first begins to show itself, and that this 

 is not improbablj' due to the lingering influence 

 of the original polar displacement of the egg- 

 nucleus at the time of maturation and impreg- 

 nation. While the germinal vesicle, or rather 

 what represents it, actually returns to the 

 centre of the deutoplasm-laden ovum in these 

 forms, maj' it not be that a path of germinal 

 matter has remained over in the track of its 

 original outward passage, through which it 

 could return to undergo the first cleavage, 

 shortlj' after which its segments were again 

 repelled towards the germinal pole ? 



The mode of evolution of the yelk is of great 

 interest, and doubtless occurred through the 

 working of natural selection. It is evidentlj- 

 adaptive in character ; and the necessitj' for its 

 presence as an appendage of the egg grew out 

 of the exigencies of the struggle for existence. 

 The lower, hollow vegetative cell of a mero- 

 blastic egg, such as shown in fig. 4, is, to all 

 intents and purposes, comparable to a fat cell, 

 or to an endosperm cell of a seed containing 

 stored reserve material, which maj- be, for the 

 most part, in an absolutelj' non-contractile or 

 static condition, like the oval globoids of the 

 egg of Lepidosteus. John A. Ryder. 



BALTIMORE SURFACE-GEOLOGY. 



The ' Geology of the surface-features of the Balti- 

 more area,' ' by P. E. Uhler, bears evident marks of 

 tlie author's unfamiharity with his subject. No proof 

 is offered in support of a nuraber of assertions con- 

 cerning the age and the physical changes of the Balti- 

 more strata. After mentioning several rocks, which 

 are referred, apparently without any evidence, to the 

 Laurentian and archaeau epochs respectively, we are 

 told, that, "during the Jurassic period, these ar- 

 chaean upfolds seem to have attained their maximum 

 development." Not a particle of evidence is offered 

 in support of this assertion, which, we think, would 

 need very strong proof indeed; and we are sui'prised 

 at the facility with which the author handles ' wide- 

 spreading, while comparatively local changes,' for 

 metamorphic purposes. We also fail to see how the 

 abundance of hornblendic and pyroxene rocks is a 

 "restricted element in the structure of the Baltimore 

 rocks, which selves to give them character, and to 

 1 Johns Hopkins univ. circ, February, 1883. 



separate them broadly from members of the series 

 found in other parts of eastern North America." We 

 were not Ijefore aware that a prevalence of such rocks 

 was confined to the vicinity of Baltimore. 



Leaving the azoic rocks, the author reaches what 

 he calls the Jurassic period, and says that only the 

 upper member of this great age of reptiles, the ' Weal- 

 den,' remains within the Ballimore area. The Eng- 

 lish Wealden is considered by European geologists as 

 the equivalent of the marine Neocomian of the con- 

 tinent, tlie lowest member of the cretaceous. More- 

 over, the Wealden is a fresh and brackish water 

 formation, considered to be the local deposit at the 

 mouth of a large river ; and, as shown by Mr. Judd,i 

 the actual marine representative of the continental 

 Neocomian occurs at the south end of Filey Bay, in 

 Yorkshire. Sir A. C. Ramsay, although describing 

 the Purbeck and Wealden as a special local fresh- 

 water formation, does not hesitate to consider the 

 Wealden as the equivalent of the Neocomian. The 

 preceding facts will show that it is difficult to see why 

 Mr. Uhler uses the terra 'Wealden' in connection 

 with the .Jurassic period, or why, if the Baltimore 

 strata are the equivalents of the local fresh-water cre- 

 taceous deposit of England, he speaks of them as of 

 Jurassic age. 



Mr. Uhler, also says that in the upper Jurassic the 

 flora has made a step in advance, gymnosperms taking 

 the place of the old catamites and their relatives. 

 But this step in advance was made already in the 

 triassic keuper, where cycadites and gymnosperms 

 make their appearance. The Wealden flora belongs 

 to that degree of development of the vegetable king- 

 dom which begins with the Pihetic, and ends with 

 the lower cretaceous. This flora does not completely 

 change till we reach the lower Quadersandstein, or 

 upper greensand, where dicotyledons make their ap- 

 pearance; so that, judging on the evidence of flora 

 alone, we should have to place the Gault or lower 

 greensand also in the Jurassic.^ 



At the close of this Wealden (?) period, Mr. Uhler 

 makes the climate colder, and brings great masses of 

 ice to tear things to pieces, but gives no evidence in 

 support even of this assertion. 



RAINFALL OF UBERABA, PROVINCE OF 

 MINAS GERAES, BRAZIL. 



The following observations on the rainfall of the 

 city of Uberaba, by Friar Germano, are interesting 

 as being, so far as Icnown, the first that have ever 

 been made in the great interior Parana basin; those 

 hitherto published being either for the coast-towns 

 and the maritime range of mountains, or, if actually 

 within the interior basins, too near the margin to 

 represent accurately the rainfall of the interior. 



Uberaba is situated about 3U0 miles from the coast, 

 in -latitude 19° 44' 30" S., on the elevated grassy plains 

 between the Parana and its great tributary the Eio 

 Grande. Its position as regards the maritime range 

 and the Parana-Paraguay basin — the South-American 

 homologue of the Mississippi valley — may be com- 

 pared with that of Cincinnali, or, better, some of the 

 Obio towns on or near the divide between the Great 

 Lakes and the Obio Elver. It is at an elevation of 750 

 metres above the level of the sea, according to the 

 determination of Friar Germano. 



Tlie material is not at hand for an accurate com- 

 parison of its rainfall with that of other points where 

 observations have been recorded. It is, however, not 



1 Qaai-t. iourn. geol. 80C. Lond., xxiv. 218. 



» Heer, Monde primitif do la Sui-sse, pp. 69, 269. 



